Air compressing and heating apparatus



Nov. 23, 1965 A. ROCHE 3,219,027

- AIR COMPRESSING AND HEATING APPARATUS Filed Nov. 19, 1962 Fig.1.

I/VVE/V TOE flNDRE IQOCHE United States Patent 3,219,027 AIR COMPRESSING AND HEATING APPARATUS Andre Roche, 45 Ave. St. Gerome,

Aix en Provence, France Filed Nov. 19, 1962, Ser. No. 238,802 1 Claim. (Cl. 126-247) This is a continuation-in-part of my co-pending United States Patent Application No. 97,833 filed March 23, 1961, now abandoned.

The spraying of certain suitable paints such as cellulose lacquers can be carried out by use of a stream of compressed air which is caused to break up the paint into finely-divided droplets and to carry said droplets, as a spray, onto the surface to be covered. Where a relatively high air pressure is used, a proportion of the droplets separate from the main stream creating the fog is well known to users of spray guns. Moreover, the drops which reach the surface to be coated burst as a result of the force with which they are projected thereon. This results in a second formation of fog, and the covering power of the coating is considerably reduced.

These drawbacks have to some extent been eliminated by the use of relatively slower moving lower pressure air streams which convey the drops of paint without fogging to the surface, where it spreads itself again without the impact causing fogging. Whilst this has the advantage that no fogging occurs, and the covering power is thereby increased, it is only relatively thin and diluted paints or coatings which can be used. The requisite thinning detracts from the quality of certain paints, while others are thereby rendered unusable altogether.

This disadvantage can be overcome to a certain extent by heating the paint to lower its viscosity, and it has already been proposed to provide electrical heating elements in paint spray guns for this purpose. 7

The object of the present invention is to provide a source of compressed air, for use in conjunction with lowpressure spray guns, in which heating of the air stream is obtained automatically at the same time as the air is compressed. It is known that the act of compressing air will always result in a rise in temperature, but with the apparatus of the present invention a still further increase of temperature is obtained, for imparting to the paint, to render it free flowing and less viscous.

In the accompanying drawing:

FIG. 1 is a central vertical section through a compressor.

FIG. 2 is an elevation, partly in section, of a representative spray gun which could be used with the compressor.

The compressor shown in FIG. 1 consists of an air-tight casing 1 containing an electric motor 2 situated in an intake compartment 3. The bottom wall 4 of the intake compartment is apertured at 5. The top wall of the casing 1 is apertured at 6. The arrows 7 indicate the path of atmospheric air into a filter cover 8. The motor 2 has a spindle 9 with a pulley 10 driving a belt 11 passed about a pulley 12 secured on a shaft 13 journalled in a second compartment 14 defined by a wall 15 apertured at 16.

The compartment 14 contains a number of internal walls 17 which define three chambers 18, 18, 18. Within each chamber 18 is disposed a pair of apertured baflies 19, 19 which are spaced from each other and from the walls 17.

Three turbine impeller rotors 20 with suitably inclined blades are secured on the driven shaft 13 and are rotated by the motor at a suit-able high speed.

Each rotor 20 is positioned in spaced relationship between one of the pairs of baflies 19, 19.

On the uppermost baffle 19 there is provided a relatively 3,219,027 Patented Nov. 23, 1965 ice narrow collar 21 narrowly spaced from the shaft 13, and on each of the other bafiles 19 there is provided a relatively wider collar 22 more widely spaced from the shaft 13, each wider collar 22 receiving a packing gland 22a disposed about the shaft 23 in air-tight sealing engagement therewith.

The top wall of the casing 1 is apertured at 23 leading to a conduit 24 for passage outwardly of a stream of compressed air.

Referring now to FIG. 2, there is shown schematically a representative spray gun which comprises a nozzle 25, a first conduit 26 for leading in compressed air, and a second conduit 27 for leading in liquid paint. By the wellknown Venturi effect, the passage of an airstream through and out of the nozzle 25 causes a lowering of pressure at the lower end of the portion 28 of the paint conduit, thereby sucking paint through the conduit 27. The conduit 27 is formed as a coil 29 about the air conduit 26 and forms therewith a simple heat-exchanger. If heated air is supplied to the conduit 26, for example by connecting it to the outlet conduit 24 of the compressor of FIG. 1, the heating of the conduit 26 will be transferred to the paint passing through coil 29.

As a further refinement, a portion of the air supplied through conduit 26 may be branched oif and led into the usual paint container, thereby to force the paint up the conduit 27.

Referring now again to FIG. 1, when the motor 2 is operated, the turbine rotor is driven to produce a compression at the upper part of the compartment 14, because the turbine rotors impel the air upwards, and a reduction of pressure at the lower part thereof. Fresh atmospheric air is accordingly drawn in (see arrows 7), passes through the filter cover 8, past the motor (to cool it), through the apertures 5 and 16, and into the lowermost chamber 18.

The three assemblies of turbine rotor and associated pairs of bafiies in .a chamber 18 each constitute a separate stage of compression and heating of the air drawn in. The first stage (lowermost) receives the cold incoming air, the second (middle) stage receives partly-warmed air and heats it further and passes it to the third (uppermost) stage, the latter giving both further compression and heating and also serving to a certain extent as a means for accumulating, releasing and smoothing out the flow of heated compressed air. There is no expansion of the air stream upon entering the conduit 24 from the compressor, and accordingly the air retains its temperature until it reaches the passage 26 and coil 29 of the spray gun.

Whereas it is conventional to use pressures of the order of one to two kilogrammes per square centimetre, the apparatus of the present invention needs only to compress the air to a pressure of the order of two to three hundred grammes per square centimetre, whilst obtaining a greater rise in temperature, due to the presence of the baffles 19, than would be obtained by simple compression to the same extent.

The driving and beating of the air by each rotor 20 against and through its associated baflies causes a high degree of energy, derived from rotation of the rotor, to be transferred to the air by enforced turbulence,-whilst at the same time the air is moved generally upward-s and compressed so as to flow out at conduit 24. Layers of compressed air are formed in each of the three stages of the compressor.

The space in each chamber 18 radially beyond the turbine rotor 20 serves as a zone of accumulation, whilst the space in each chamber 18 defined between each rotor and its associated batfles, and also between those baffles and the adjacent walls 17, serve as zones of compression and heating by turbulence.

Iclaim: (d) said air compressing and heating means com- Apparatus for supplying compressed and heated air prising a rotatable shaft disposed in said common comprising: transverse passage and drivingly connected to said (a) a casing having outer walls, including a first air inlet and an air outlet and containing a motor and a 5 motor, said shaft having mounted thereon in each air chamber at least one rotatable ai-r impeller blade separate inside compartment;

(b) said compartment within said casing containing a rotatable air compressing and heating means, said compartment further comprising (1) compartment enclosing Walls having a second air inlet in communilo cation with the interior of said casing, and said air outlet to the exterior of said casing; and (2) a series of opposed inner divider walls connected to and projecting inwardly from said enclosing Walls, said passage by said blades.

References Cited by the Examiner UNITED STATES PATENTS divider walls being parallel to and spaced from each 15 1598289 8/1926 Lee 126 247 X other where they connect to said compartment en- 1682102 8/1928 Allen 126 247 closing walls and said divider Walls defining a series 246O861 2/1949 Walters 239-132 of air chambers connected by a common passage 2613995 10/1952 Relphold 239 351 transverse to said divider walls and connecting Sa d 2683448' 7/1954 smlth 126-247 ond air inlet and said air outlet; 20 3075514 1/1963 Paugh 126-247 (c) said motor within said casing situated between said FOREIGN PATENTS first air inlet and said second air inlet to said com- 957,200 8/1949 France.

partment whereby air passing into and through said first air inlet surrounds and cools said motor and thereafter passes in heated condition through the 25 common passage of said compartment and out of said air outlet; and

FREDERICK L. MATTESON, JR., Primary Examiner.

JAMES W. WESTHAVER, Examiner. 

